Re: Truncating/vacuuming relations on full tablespaces - Mailing list pgsql-hackers

From Robert Haas
Subject Re: Truncating/vacuuming relations on full tablespaces
Date
Msg-id CA+TgmoZHLKxiL39Xfjr8zYaOzG4cXeN-U=oCFRRQ_Lp+JhmRKQ@mail.gmail.com
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In response to Re: Truncating/vacuuming relations on full tablespaces  (Asif Naeem <anaeem.it@gmail.com>)
List pgsql-hackers
On Mon, Jun 20, 2016 at 7:28 AM, Asif Naeem <anaeem.it@gmail.com> wrote:
> Thank you for useful suggestions. PFA patch, I have tried to cover all the
> points mentioned.

Thanks for the new patch.  I think that you have failed to address
this point from my previous review:

# I see why you changed the calling convention for visibilitymap_pin()
# and RecordPageWithFreeSpace(), but that's awfully invasive.  I wonder
# if there's a better way to do that, like maybe having vacuumlazy.c ask
# the VM and FSM for their length in pages and then not trying to use
# those functions for block numbers that are too large.

The patch has gotten a lot smaller, and that's clearly good, but
introducing extended versions of those functions still seems like a
thing we should try to avoid. In particular, there's no way this hunk
is going to be acceptable:

@@ -286,6 +299,10 @@ visibilitymap_set(Relation rel, BlockNumber
heapBlk, Buffer heapBuf,    if (BufferIsValid(heapBuf) && BufferGetBlockNumber(heapBuf) != heapBlk)        elog(ERROR,
"wrongheap buffer passed to visibilitymap_set");
 

+    /* In case of invalid buffer just return */
+    if(vmBuf == InvalidBuffer)
+        return;
+    /* Check that we have the right VM page pinned */    if (!BufferIsValid(vmBuf) || BufferGetBlockNumber(vmBuf) !=
mapBlock)       elog(ERROR, "wrong VM buffer passed to visibilitymap_set");
 

You're going to have to find a different approach there.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company



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